JP2000057561A - Magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic tape adaptive for a magnetic recording and reproducing system capable of high density recording, exhibiting excellent electromagnetic transducing characteristic, handling property and traveling durability and particularly advantageous for recording computer data. SOLUTION: The magnetic tape has a magnetic layer containing ferromagnetic powder and a binder on one surface of a long-length support and a back coat layer containing carbon black and a binder on another surface of the long-length support, is 3-10 μm in the total thickness and is constituted so that the radius of curvature of curl of the magnetic tape in the longitudinal direction is >=10 mm and the curl of the tape in the width direction is curved projectingly to the magnetic layer side and the radius of curvature is >=40 mm. A magnetic tape provided with a non-magnetic layer between the support and the magnetic layer has the same constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape which is advantageously used as an external recording medium for recording computer data.

[0002]

2. Description of the Related Art In recent years, in a magnetic recording / reproducing system for a magnetic recording medium such as a magnetic tape (backup tape) for recording computer data, a recording wavelength has been shortened so as to record at higher density. There is a tendency that the track width at the time of recording is narrowed, and the processing speed of recording and reproduction is increased so that a large amount of information can be processed faster. On the other hand, the magnetic tape itself
In order to achieve a larger recording capacity, there is a tendency to become thinner. Therefore, even with such a thinned magnetic tape, higher running durability is required than ever.
In systems developed for high-density recording, slight deformation of the tape may hinder stable running, or may affect the state of contact with the magnetic head (so-called head contact), resulting in lower output. Problems, such as the cause of the occurrence of, are also likely to occur. For this reason, it is desired that even a thin magnetic tape be deformed as little as possible.

In general, a magnetic tape has a configuration in which a magnetic layer is provided on a flexible support such as a synthetic resin. Also,
In order to achieve a higher recording density, a magnetic tape having a structure in which a nonmagnetic layer is provided on a support and a thin magnetic layer is further provided thereon has been proposed. In general, it is preferable that the surface of the magnetic layer is smooth in order to maintain good sensitivity, but in order to prevent turbulence and deterioration in running performance due to the smoothing, the surface of the support opposite to the magnetic layer is preferably used. Is provided with a back coat layer. A magnetic tape having a structure in which a magnetic layer is provided on one side of a support and a back coat layer is provided on the other side is disclosed in, for example, JP-A-5-21714.
No. 6 and No. 6-215350. Further, a magnetic tape having a structure in which a nonmagnetic layer and a thin magnetic layer are sequentially provided on one surface of a support, and a back coat layer is provided on the other surface of the support, is disclosed in, for example, JP-A-5-182178. No. 6,086,045.

[0004]

Generally, when the thickness of a magnetic tape becomes thinner, compared with a thick magnetic tape,
Due to the lack of rigidity of the tape itself, stress is applied by elongation, compression, or drying in the process of manufacturing the magnetic tape, which tends to cause curl in the length and width directions of the tape. In particular, the curl (coiling) in the length direction of the magnetic tape tends to be curled with the magnetic layer side outward, as the voids in the magnetic layer crushed by compression in the calendering process try to return to the original state. Become. On the other hand, the curl (cupping) in the width direction of the tape is caused by the contraction force of the binder in the back coat layer acting as residual stress.
A convex curl tends to occur on the magnetic layer side.

The present inventors have examined the effects of the above-mentioned curl on the electromagnetic conversion characteristics and the handling of the tape with respect to the thinned magnetic tape. According to the study, in a recent magnetic recording system, the handling tension in the system is set low as the tape becomes thinner. For this reason, it turned out that the bad influence by curl became more likely to appear than before. In other words, when the curl in the length direction of the tape is increased, the contact force between the magnetic layer of the magnetic tape and the magnetic head is weakened, which leads to fluctuation in output. Further, when handling the tape in the manufacturing process, such a problem that the tape is curled and the working efficiency is reduced is likely to be accompanied. Especially in the slitting process, the tape is turned upside down when winding up the slit tape,
Significantly makes workability difficult. On the other hand, if the curl in the width direction with the magnetic layer side of the tape protruding increases, the contact state with the head at the edge of the tape weakens, so the output also decreases, and the regulation of the running guide also weakens. In addition, the vertical movement of the tape during running becomes large, and off-track easily occurs. In particular, the curl in the width direction of the tape becomes remarkable when relatively hard nitrocellulose is used as a binder of the back coat layer in order to maintain high running performance, and the output may be easily reduced accordingly. all right.

Japanese Patent Application Laid-Open No. Hei 5-307731 discloses that the degree of curl in the width direction of a magnetic tape (the amount of curvature in which the magnetic layer side becomes convex) is reduced to 0.3 to 1/2 inch in the width direction of the tape.
By adjusting the amount of curvature to be 0.7 mm (corresponding to a radius of curvature of 56 mm to 29 mm), even when the thickness of the tape is reduced, the output is less reduced and the dropout is less likely to occur. There has been proposed a magnetic tape which exhibits conversion characteristics and exhibits high durability with little deformation or damage due to running of the tape in the system. However, here, only the curl in the width direction of the magnetic tape is studied, and the problem of the curl in the length direction of the magnetic tape is not mentioned at all.

An object of the present invention is to provide a magnetic tape suitable for a magnetic recording / reproducing system capable of high-density recording and exhibiting good electromagnetic conversion characteristics, handling properties, and running durability, and particularly advantageous for computer data recording. To provide.

[0008]

SUMMARY OF THE INVENTION The present invention comprises a long support having a magnetic layer containing ferromagnetic powder and a binder on one side and carbon black and a binder on the other side. A magnetic tape having a back coat layer and a total thickness of 3 to 10 μm, wherein the radius of curvature of the curl in the longitudinal direction of the magnetic tape is 10 mm or more, and the curl in the width direction of the tape is convex toward the magnetic layer. A magnetic tape (first aspect) characterized in that the magnetic tape has a curved shape and the radius of curvature is 40 mm or more.

The present invention also relates to a non-magnetic layer having a thickness of 0.5 to 2.5 μm which is substantially non-magnetic and contains a non-magnetic powder and a binder on one side of a long support. A magnetic layer having a thickness of 0.05 to 1.0 μm containing a powder and a binder, and a back coat layer containing a carbon black and a binder on the other side having a total thickness of 3 to 10 μm.
μm magnetic tape, the radius of curvature of the curl in the longitudinal direction of the magnetic tape is 10 mm or more, and the curl in the width direction of the tape has a convex curve toward the magnetic layer side,
There is also a magnetic tape (second embodiment) characterized in that its curvature radius is 40 mm or more.

In the present specification, the radius of curvature of the curl in the longitudinal direction of the magnetic tape is such that a magnetic tape having a desired width and a length of 1 m is fixed at one end to a test environment (23 ° C. ± 2 ° C., 50% ± 10% RH). After hanging for 3 hours with the other end as a free end,
It means the radius of curvature of the curl generated when a measurement sample is prepared by cutting out a length of 35 mm below the center of the sample and standing on a flat surface with the side of the tape facing down.

The radius of curvature of the curl in the width direction of the magnetic tape means a value obtained by the following procedure. A 1m long magnetic tape with the desired width was tested in a test environment (23 ° C ± 2 ° C, 50%
± 10% RH) with one end fixed and the other end free.
After suspending for a period of time, the sample is cut out so that the length above and below the center thereof is 250 mm at a time, and the length is 500 mm, to prepare a measurement sample. As shown in FIG. 1 of the accompanying drawings, one end of the tape is fixed with the magnetic layer facing upward, and a 3.5 g weight is hung at the other end via a roller (diameter: 10 mm). The distance between the fixed end of the tape and the center of the roller is 200
mm. The optical displacement meter is scanned in the width direction of the tape at a position 100 mm from the fixed end of the tape, and the difference between the center position in the width direction of the tape and the position of the edge of the tape is measured. The radius of curvature of the curl in the width direction of the tape means a value obtained from this value and the width of the tape.

The magnetic tape of the present invention preferably has the following aspects. (1) The radius of curvature of the curl in the longitudinal direction of the magnetic tape is 14
mm or more (more preferably 17 mm or more, particularly preferably 20 mm or more, most preferably 25 mm or more)
It is. (2) The radius of curvature of the curl in the width direction of the magnetic tape is 45 m.
m or more (more preferably 60 mm or more, particularly preferably 100 mm or more, and most preferably 150 mm or more). (3) The Young's modulus in the longitudinal direction of the support is 1.1 times to 1.8 times (more preferably, 1.2 times) the Young's modulus in the width direction.
1.8 times, particularly preferably 1.3 times to 1.8 times). (4) The Young's modulus in the longitudinal direction of the support is 750 to 950 k
g / mm ² (more preferably, 780-950 kg / m
m ² , particularly preferably 850 to 950 kg / mm ² )
It is. (5) The support has a thickness of 2.0 to 8.0 μm (more preferably 3.0 to 7.0 μm, particularly preferably 4.0 to 7.0 μm).
6.5 μm). (6) The support is polyethylene naphthalate.

(7) The binder of the back coat layer contains a phenoxy resin and / or a vinyl chloride resin. (8) The thickness of the back coat layer is 0.1 to 1.0 μm (more preferably, 0.2 to 0.8 μm, particularly preferably,
0.3-0.6 μm). (9) The back coat layer contains carbon black and a hard inorganic powder having a Mohs hardness of 5 to 9. (10) The carbon black includes two types of carbon blacks having different average particle sizes of fine carbon black of 10 to 20 μm and coarse carbon black of 230 to 300 μm. (11) The hard inorganic powder having a Mohs hardness of 5 to 9 is α-alumina or α-iron oxide. (12) The total thickness of the magnetic tape is 4.0 to 9.5 μm
(More preferably, 4.5 to 9.0 μm, particularly preferably 5.0 to 8.5 μm). (13) A magnetic tape for recording computer data.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic tape of the present invention has a curvature radius of 10 mm or more in the longitudinal direction, and the curl in the width direction of the tape has a convex curve toward the magnetic layer. The radius of curvature is 40 mm or more. The radius of curvature of the curl in the longitudinal direction of the magnetic tape is preferably 14 mm or more (more preferably, 17 mm or more, particularly preferably, 20 mm or more, and most preferably,
25 mm or more). The radius of curvature of the curl in the width direction of the magnetic tape is preferably 45 mm or more (more preferably 60 mm or more, particularly preferably 100 mm or more, and most preferably 150 mm or more).

The magnetic tape according to the present invention has a long support having a magnetic layer containing a ferromagnetic powder and a binder on one side and a carbon layer on the other side. A first embodiment having a back coat layer containing black and a binder, and a substantially non-magnetic thickness of 0.5 to 2 containing a non-magnetic powder and a binder on one side of an elongated support. .
A 5 μm non-magnetic layer and a 0.05-1.0 μm thick magnetic layer containing ferromagnetic powder and a binder in this order, and a back coat layer containing carbon black and a binder on the other side. A second embodiment is included.

First, the magnetic tape of the first embodiment will be described. Hereinafter, the support, the magnetic layer, and the back coat layer will be described in detail in order. As the support, those conventionally used as a support material for a magnetic tape can be used, and a non-magnetic support is particularly preferable. Examples of these include polyesters (eg, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), a mixture of polyethylene terephthalate and polyethylene naphthalate, a polymer containing an ethylene terephthalate component and an ethylene naphthalate component), polyolefins (Eg, polypropylene), cellulose derivatives (eg, cellulose diacetate, cellulose triacetate),
Synthetic resin films such as polycarbonate, polyamide (particularly aromatic polyamide, aramid), and polyimide (particularly wholly aromatic polyimide) can be given. Among these, polyethylene naphthalate (PEN) is preferred. The Young's modulus in the longitudinal direction of the support is 1.1 times to 1.8 times (more preferably, 1.2 times to 1.8 times, particularly preferably, 1.3 times to 1.times.) The Young's modulus in the width direction. 8 times). The support has a Young's modulus in the longitudinal direction of 750 to 950 kg / mm ² (more preferably, 7 to 950 kg / mm ² ).
80 to 950 kg / mm ² , particularly preferably 850 to 950 kg / mm ²
950 kg / mm ² ). The thickness of the support is 2.0 to 8.0 μm (more preferably 3.0 to 8.0 μm).
To 7.0 μm, particularly preferably 4.0 to 6.5 μm)
Is preferably within the range.

The magnetic layer is basically formed from a ferromagnetic powder and a binder. Further, the magnetic layer usually contains a lubricant, a conductive powder (eg, carbon black), and an abrasive. As the ferromagnetic powder, for example, γ-F
_{e 2 O 3, Fe 3 O} 4, FeOx (x = 1.33~1.
5), CrO ₂ , Co-containing γ-Fe ₂ O ₃ , Co-containing F
eOx (x = 1.33 to 1.5), ferromagnetic metal powder (ferromagnetic alloy powder), and plate-like hexagonal ferrite powder. In the present invention, it is preferable to use a ferromagnetic metal powder or a plate-like hexagonal ferrite powder as the ferromagnetic powder. Particularly preferred are ferromagnetic metal powders.

The ferromagnetic metal powder preferably has a particle specific surface area of 30 to 70 m ² / g, and a crystallite size determined by X-ray diffraction is 50 to 300 Å. If the specific surface area is too small, it will not be possible to sufficiently cope with high-density recording, and if it is too large, it will not be possible to sufficiently disperse, and it will not be possible to form a magnetic layer having a smooth surface, and it will also be impossible to cope with high-density recording. .

The ferromagnetic metal powder needs to contain at least Fe, specifically, Fe, Fe--Co, F
It is a simple metal or an alloy mainly composed of e-Ni, Fe-Zn-Ni or Fe-Ni-Co. Note that Fe alone may be used. Regarding the magnetic properties of these ferromagnetic metal powders, in order to achieve a high recording density, the saturation magnetization (saturation magnetic flux density) (σs) is 110 emu / g or more.
Preferably it is 120 emu / g or more and 170 emu / g or less. The coercive force (Hc) is 1400 to 2500 Oersted (Oe) (preferably 1500 to 2400
Oe). Further, the major axis length of the powder (that is, the average particle size) determined by a transmission electron microscope is 0.
The axis ratio (major axis length / minor axis length, acicular ratio) is 5 μm or less, preferably 0.01 to 0.3 μm, and is 5 to 20, preferably 5 to 15. In order to further improve the properties, non-metals such as B, C, Al, Si, and P, or salts or oxides thereof may be added to the composition. Usually, an oxide layer is formed on the particle surface of the metal powder for chemical stability.

The plate-like hexagonal ferrite powder has a specific surface area of 25 to 65 m ² / g, a plate ratio (plate diameter / plate thickness) of 2 to 15, and a particle size (plate diameter) of 0.02 to 0.02. 1.
0 μm. For the same reason as the ferromagnetic metal powder, high-density recording becomes difficult even if the particle size of the plate-like hexagonal ferrite powder is too large or too small. The plate-like hexagonal ferrite is a ferromagnetic material having a plate shape and an easy axis of magnetization in a direction perpendicular to the plate surface, and specifically, barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and the like. And the like. Of these, cobalt-substituted barium ferrite and cobalt-substituted strontium ferrite are particularly preferred. If necessary, elements such as In, Zn, Ge, Nb, and V may be added to the plate-like hexagonal ferrite in order to further improve its properties. Regarding the magnetic properties of these plate-like hexagonal ferrite powders, in order to achieve a high recording density, the above-described particle size is required and the saturation magnetization (σs)
Is at least 50 emu / g or more, preferably 53 em
u / g or more. The coercive force (Hc) is 700 to 20
00 Oersted (Oe), 900 to 16
It is preferably in the range of 00 Oe.

The water content of the ferromagnetic powder is 0.01 to 2% by weight.
It is preferable that It is preferable to optimize the water content depending on the type of the binder. The pH of the ferromagnetic powder is preferably optimized by a combination with the binder used, and the pH is usually in the range of 4 to 12, and preferably in the range of 5 to 10. The ferromagnetic powder preferably has a part of its surface coated with Al, Si, P or an oxide thereof, if necessary. Surface treatment may be performed. The amount used for the surface treatment is usually 0.1 to 10% by weight based on the ferromagnetic powder. Since the ferromagnetic powder coated in this manner can suppress the adsorption of a lubricant such as a fatty acid to 100 mg / m ² or less, a desired effect can be achieved even if the amount of the lubricant added to the magnetic layer is reduced. . Ferromagnetic powder contains soluble Na, Ca, Fe, Ni,
And Sr may be included as inorganic ions, but the content is preferably as small as possible. Usually, if it is 500 ppm or less, there is no influence on the characteristics.

The lubricant is added to alleviate the friction between the surface of the magnetic layer and the magnetic head by oozing to the surface of the magnetic layer, and to maintain a smooth sliding contact state. Examples of the lubricant include a fatty acid and a fatty acid ester. Examples of fatty acids include acetic acid, propionic acid, 2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, arachiic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and palmitoleic acid And a mixture thereof.

Examples of the fatty acid ester include butyl stearate, sec-butyl stearate, isopropyl stearate, butyl oleate, amyl stearate, 3-methylbutyl stearate, 2-ethylhexyl stearate, and 2-hexyldecyl. Stearate,
Acyl butyl palmitate, 2-ethylhexyl myristate, a mixture of butyl stearate and butyl palmitate, oleyl oleate, butoxyethyl stearate, 2-butoxy-1-propyl stearate, dipropylene glycol monobutyl ether with stearic acid And various ester compounds such as diethylene glycol dipalmitate, hexamethylene diol acylated with myristic acid to form a diol, and glycerin oleate. The above fatty acids and fatty acid esters can be used alone or in combination of two or more compounds. The usual content of the lubricant is 0.2 to 20 parts by weight (preferably 0.5 to
10 parts by weight).

[0024] Carbon black is a reduction in the surface electric resistance of the magnetic layer (R _S), reduction of the dynamic friction coefficient (mu _K value), improvement of running durability, and various such to ensure a smooth surface of the magnetic layer It is added for the purpose. Carbon black has an average particle diameter of 5 to 350 mμ (more preferably, 10 to 3 mμ).
(00 μm). The specific surface area is 5 to 500 m ² / g (more preferably, 50 to 500 m ² / g).
It is preferably 300 m ² / g). Two or more carbon blacks having different average particle diameters can be used. DBP oil absorption is 10 to 1000 ml / 10
0g (more preferably 50-300ml / 100g)
Is preferably within the range. The pH is 2 to 10,
The water content is 0.1-10%, and the tap density is 0.1%.
It is preferably from 1 to 1 g / cc.

As the carbon black, those obtained by various production methods can be used. Examples of carbon black that can be used include furnace black, thermal black, acetylene black, channel black and lamp black. Specific examples of carbon black products include BLACKPEARLS 2000, 1
300, 1000, 900, 800, 700, VULC
AN XC-72 (above, manufactured by Cabot Corporation), # 35,
# 50, # 55, # 60 and # 80 (all manufactured by Asahi Carbon Co., Ltd.), # 3950B, # 3750B, # 3250
B, # 2400B, # 2300B, # 1000, # 90
0, # 40, # 30, and # 10B (all manufactured by Mitsubishi Chemical Corporation), CONDUCTEX SC, RAVEN
150, 50, 40, 15 (all manufactured by Columbia Carbon Co., Ltd.), Ketjen Black EC, Ketjen Black ECDJ-500 and Ketjen Black ECDJ-
600 (all manufactured by Lion Aguso Co., Ltd.).

The usual addition amount of carbon black is in the range of 0.1 to 30 parts by weight (preferably 0.2 to 15 parts by weight) per 100 parts by weight of the ferromagnetic powder.

Examples of the abrasive include fused alumina, silicon carbide, chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite). be able to. These abrasives have a Mohs hardness of 5 or more (preferably 6 or more) and an average particle size of 0.05 to 1 μm (more preferably 0.2 to 0.8 μm, particularly 0 to 0 μm). .2 to 0.5 μm). The amount of the abrasive is usually 3 to 25 parts by weight (preferably 3 to 20 parts by weight) per 100 parts by weight of the ferromagnetic powder.
Parts by weight).

Examples of the binder for the magnetic layer include thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof. Examples of thermoplastic resins include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid,
Acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, and a polymer containing as a structural unit, or a copolymer containing vinyl ether can be given. . As the copolymer, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer,
Vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride copolymer, acrylate-styrene copolymer, methacrylate-acrylonitrile copolymer, methacrylate -Vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, styrene-butadiene copolymer, chlorovinyl ether-acrylic acid ester copolymer be able to.

In addition to the above, polyamide resins, cellulose resins (cellulose acetate butyrate, cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resins, polyurethane resins, various rubber resins Etc. can also be used.

Examples of the thermosetting resin or reactive resin include, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic reaction resin, formaldehyde resin, silicone resin, and epoxy resin. Examples thereof include a polyamide resin, a mixture of a polyester resin and a polyisocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, and a mixture of a polyurethane and a polyisocyanate.

Examples of the polyisocyanate include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Examples include isocyanates such as 5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, and triphenylmethane triisocyanate, products of these isocyanates and polyalcohols, and polyisocyanates formed by condensation of isocyanates.

Known polyurethane resins having a structure such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used as the polyurethane resin.

In the present invention, the binder for the magnetic layer is a vinyl chloride resin, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a vinyl chloride-vinyl acetate-maleic anhydride copolymer. It is preferable that the resin is composed of a combination of at least one resin selected from coalesced and nitrocellulose and a polyurethane resin, or a combination of these with a polyisocyanate as a curing agent.

As the binder, -COO may be used if necessary in order to obtain better dispersibility and durability of the obtained layer.
_{M, -SO 3 M, -OSO 3} M, -P = O (OM) 2,
-O-P = O (OM) 2 (M represents a hydrogen atom or an alkali metal,.), - OH, -NR 2, -N + R 3
(R represents a hydrocarbon group.), An epoxy group, -SH,
It is preferable to use at least one polar group selected from —CN or the like by copolymerization or addition reaction.
Such a polar group is added to the binder at 10 ^-1 to 10 ^-8 mol / g.
(More preferably, 10 ⁻² to 10 ⁻⁶ mol / g).

The binder in the magnetic layer is usually 5 to 50 parts by weight (preferably 10 to 50 parts by weight) based on 100 parts by weight of the ferromagnetic powder.
30 parts by weight). When a vinyl chloride resin, a polyurethane resin, and a polyisocyanate are used in combination as a binder in the magnetic layer, the vinyl chloride resin is 5 to 70% by weight, and the polyurethane resin is 2 to 50% by weight in all the binders. % And the polyisocyanate is preferably present in an amount ranging from 2 to 50% by weight.

A dispersant can be added to the coating solution for forming the magnetic layer in order to disperse the magnetic powder in the binder. If necessary, a plasticizer, conductive particles (antistatic agent) other than carbon black, an antifungal agent, and the like can be added to each layer. As the dispersant, for example, caprylic acid, capric acid, lauric acid,
Fatty acids having 12 to 18 carbon atoms such as myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid (RCOOH, where R is alkyl having 11 to 17 carbon atoms) Group,
Or an alkenyl group), a metal soap of an alkali metal or an alkaline earth metal of the fatty acid, a fluorine-containing compound of the fatty acid ester, an amide of the fatty acid,
Polyalkylene oxide alkyl phosphate, lecithin, trialkyl polyolefin oxy quaternary ammonium salt (alkyl has 1 to 5 carbon atoms, olefin is ethylene, propylene, etc.), sulfate, copper phthalocyanine, etc. it can. These may be used alone or in combination. The dispersant is added to the magnetic layer in a range of 0.5 to 20 parts by weight based on 100 parts by weight of the binder.

The back coat layer is formed from carbon black and a binder. It is preferable that an inorganic powder or a lubricant is further added. Carbon black is
It is preferable to use a combination of two types having different average particle sizes. In this case, the average particle size is 1
It is preferable to use a combination of fine carbon black having a particle size of 0 to 20 μm and coarse carbon black having an average particle size of 230 to 300 μm. In general, the surface electric resistance of the back coat layer can be set low and the light transmittance can be set low by the addition of the fine carbon black as described above. Some magnetic recording devices utilize the light transmittance of the tape and use it as an operation signal. In such a case, the addition of fine carbon black is particularly effective. In addition, fine particle carbon black generally has excellent holding power for a liquid lubricant, and contributes to a reduction in friction coefficient when used in combination with a lubricant. On the other hand, the coarse-grained carbon black having a particle size of 230 to 300 mμ has a function as a solid lubricant, and also forms fine protrusions on the surface of the back layer to reduce the contact area,
It contributes to a reduction in friction coefficient.

The following are specific products of the particulate carbon black. RAVE
N2000B (18mμ), RAVEN 1500B (1
7mμ) (all manufactured by Columbia Carbon Co., Ltd.), BP80
0 (17mμ) (Cabot), PRINTEX9
0 (14mμ), PRINTEX95 (15mμ), P
RINTEX85 (16mμ), PRINTEX75
(17 mμ) (all manufactured by Degussa), # 3950 (16
mμ) (manufactured by Mitsubishi Chemical Corporation). Examples of specific products of coarse-grained carbon black include thermal black (270 mμ) (manufactured by Kahn Carb), RAVEN M
TP (275 mμ) (manufactured by Columbia Carbon Co., Ltd.) can be mentioned.

In the case of using two types having different average particle sizes in the back coat layer, 10 to 20 μm
Is preferably in the range of 98: 2 to 75:25, and more preferably 95: 5. ~ 85: 15. The content of carbon black (total amount) in the back coat layer is usually 3 parts by weight with respect to 100 parts by weight of the binder.
0 to 110 parts by weight, preferably 50 to 9 parts by weight.
The range is 0 parts by weight.

The addition of the hard inorganic powder having a Mohs hardness of 5 to 9 enhances the strength of the back coat layer and improves running durability. When this is used together with carbon black, it is less deteriorated even by repeated sliding, and becomes a strong backcoat layer. In addition, the addition of the inorganic powder provides an appropriate polishing force, and reduces the adhesion of shavings to the tape guide pole and the like. The hard inorganic powder has an average particle size of 80 to 250 mμ (more preferably 10 to 250 mμ).
(0 to 210 mμ).

Examples of the hard inorganic powder having a Mohs hardness of 5 to 9 include α-iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ ). These powders may be used alone or in combination. Of these, α-iron oxide or α-alumina is preferred. The content of the hard inorganic powder is usually 3 to 30 parts by weight based on 100 parts by weight of carbon black,
Preferably, it is 3 to 20 parts by weight.

The back coat layer may contain a lubricant. The lubricant can be appropriately selected from the lubricants described for the magnetic layer. In the back coat layer, the lubricant is usually added in the range of 1 to 5 parts by weight based on 100 parts by weight of the binder. Further, the dispersant described in the magnetic layer can be added to the back coat layer. The amount of the dispersant added can be the same as the amount added to the magnetic layer.

As the binder for the back coat layer, the binder described for the magnetic layer can be used. Examples of usable binders include nitrocellulose resin, vinyl chloride resin, phenoxy resin, polyurethane resin, polyester resin, and polyisocyanate as a curing agent. In the present invention, a combination of a vinyl chloride resin and / or a phenoxy resin (40 to 90% by weight, preferably 55 to 80% by weight of the total binder), a polyurethane resin, a polyester resin, and a polyisocyanate as a curing agent is used. It is preferred to use. The vinyl chloride resin and the phenoxy resin have a smaller contraction force than the nitrocellulose resin, and therefore, by using these resins, it is possible to suppress curling in the width direction of the magnetic tape. The binder of the back coat layer is carbon black 100
5 to 250 parts by weight (preferably,
10 to 200 parts by weight).

Next, the magnetic tape of the second embodiment will be described. The magnetic tape of the second embodiment basically has a configuration in which a non-magnetic layer is further provided between the support and the magnetic layer in the magnetic tape of the first embodiment described above. Therefore, except for the nonmagnetic layer, the magnetic tape can be configured in the same manner as the magnetic tape of the first embodiment.

The non-magnetic layer is a substantially non-magnetic layer containing a non-magnetic powder and a binder. The non-magnetic layer needs to be substantially non-magnetic so as not to affect the electromagnetic conversion characteristics of the magnetic layer thereon. Is not a problem. The nonmagnetic layer usually contains a lubricant in addition to these components.

Examples of the non-magnetic powder used in the non-magnetic layer include non-magnetic inorganic powder and carbon black. The nonmagnetic inorganic powder is preferably relatively hard, and preferably has a Mohs hardness of 5 or more (more preferably 6 or more). Examples of these non-magnetic inorganic powders include α-alumina, β-alumina, γ-alumina,
Silicon carbide, chromium oxide, cerium oxide, α-iron oxide,
Examples include corundum, silicon nitride, titanium carbide, titanium dioxide, silicon dioxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, and barium sulfate. These can be used alone or in combination. Among these, titanium dioxide, α-alumina, α-iron oxide or chromium oxide is preferred. The average particle size of the nonmagnetic inorganic powder is 0.01 to 1.0 μm (preferably 0.01 to 0.5 μm, particularly 0.02 to 0.1 μm).
m).

The carbon black is added for the purpose of imparting conductivity to the magnetic layer to prevent electrification and ensuring a smooth surface property of the magnetic layer formed on the non-magnetic layer. As the carbon black used in the non-magnetic layer, the above-described carbon black that can be contained in the magnetic layer can be used. However, the carbon black used in the nonmagnetic layer preferably has an average particle diameter of 35 mμ or less (more preferably, 10 to 35 mμ). The normal addition amount of carbon black is 100% of all non-magnetic inorganic powder.
3 to 20 parts by weight with respect to parts by weight, preferably,
It is 4 to 18 parts by weight, more preferably 5 to 15 parts by weight.

As the lubricant, the fatty acid or fatty acid ester described for the magnetic layer of the magnetic tape of the first embodiment can be used. The usual amount of the lubricant is based on 100 parts by weight of the total nonmagnetic powder in the nonmagnetic layer.
It is in the range of 0.2 to 20 parts by weight.

As the binder for the nonmagnetic layer, the binder described for the magnetic layer can be used. The binder is usually in the range of 5 to 50 parts by weight (preferably 10 to 30 parts by weight) based on 100 parts by weight of the nonmagnetic powder of the nonmagnetic layer. When a non-magnetic layer is used in combination with a vinyl chloride resin, a polyurethane resin, and polyisosinate as a binder, the total binder contains 5 to 70% by weight of the vinyl chloride resin and 2 to 50% by weight of the polyurethane resin. % And the polyisocyanate is preferably present in an amount ranging from 2 to 50% by weight. In the non-magnetic layer, optional components that can be added to the magnetic layer described above can be added.

The method for producing the magnetic tape of the present invention will be described. The magnetic tape of the present invention can be manufactured by introducing a processing step for reducing the curl state in the longitudinal direction and the curl state in the width direction, specifically, a heat treatment step into the conventional manufacturing step. The heat treatment step is preferably introduced before (after the drying step), after the calendar treatment step, or before and after the calendar treatment step in the magnetic tape manufacturing step.

The magnetic tape of the present invention can be manufactured according to the following steps. (Step 1) i) A coating solution for each of the magnetic layer, the non-magnetic layer, and the back coat layer is prepared. ii) The prepared coating solution, in the case of the magnetic tape of the first embodiment, the magnetic layer, in the case of the magnetic tape of the second embodiment,
The coating solution for forming the non-magnetic layer and the magnetic layer is applied to one side of the long support. In the case of the magnetic tape of the second embodiment, the method of forming the magnetic layer and the non-magnetic layer is not particularly limited, but the magnetic layer is formed by applying a coating solution for a non-magnetic layer on a support and then forming the coating layer ( It is preferably formed by using a so-called wet-on-wet coating method in which a coating liquid for a magnetic layer is coated on the non-magnetic layer while it is in a wet state.

Examples of the above-mentioned wet-on-wet coating method include the following methods. (1) A non-magnetic layer is first formed on a support using a gravure coating, a roll coating, a blade coating, or an extrusion coating device. Method for forming a magnetic layer by a lug coating device (Japanese Patent Application Laid-Open No. 60-23817)
9, JP-B 1-46-186, and JP-A-2-265
672). (2) A method in which a magnetic layer and a non-magnetic layer are formed almost simultaneously on a support using a coating apparatus comprising a single coating head having two coating liquid slits (Japanese Patent Laid-Open No. 63-880)
No. 80, JP-A-2-17921 and JP-A-2-26
5672). (3) A method in which a magnetic layer and a non-magnetic layer are formed almost simultaneously on a support using an extrusion coating apparatus with a backup roller (see Japanese Patent Application Laid-Open No. 2-174965). The non-magnetic layer and the magnetic layer are preferably formed using a simultaneous multilayer coating method. iii) After forming the magnetic layer, or the non-magnetic layer and the magnetic layer, drying is performed.

(Step 2) iv) Next, a coating liquid for forming a back coat layer is applied to the other side of the support to form a back coat layer. v) After forming the back coat layer, dry. Through the above steps, a wide and long magnetic recording laminate is manufactured.

(Step 3) vi) Heat treatment I is performed. The conditions of the heat treatment I are preferably such that the tension of the continuously running magnetic recording laminate is in a range of 1 to 5 kg / m and a temperature of 80 to 150 ° C (more preferably 85 to 130 ° C). Note that the heat treatment here depends on the heating temperature, but is preferably performed in a short time so that each layer is not excessively cured. Specifically, the time is preferably in the range of 1 second to 1 minute (more preferably, 1 second to 30 seconds). vii) Wind the magnetic recording laminate on a roll. viii) Perform calendar processing.

(Step 4) ix) Heat treatment II is performed. In this case, the heat treatment II is performed by storing at a relatively low heating temperature for a long time while being wound on a roll. The specific processing conditions are preferably in the range of 60 to 80 ° C. in the state of a roll (with a tension of 2 to 5 kg / m), and the heat treatment time is 15 to 70 hours (more preferably, 20 to 50 hours). x) Cut to predetermined width. xi) Wrap in a predetermined cartridge to produce a magnetic tape.

The surface of the back coat layer of the magnetic tape of the present invention tends to be transferred to the surface of the magnetic layer while the tape is wound. For this reason, it is preferable that the surface of the back coat layer also has relatively high smoothness. The surface of the back coat layer of the magnetic tape of the present invention has a surface roughness Ra.
(Center line average roughness with a cutoff of 0.08 mm)
It is preferable that the thickness be adjusted to be in the range of 003 to 0.060 μm. In addition, the surface roughness is usually determined by the material of the calender roll used, its surface properties, the pressure, etc., in the surface treatment step by the calender after the formation of the coating film.
Can be adjusted.

The magnetic layer of the magnetic tape according to the first embodiment has a thickness of 1.0 to 3.0 μm (more preferably, 1.2 to 3.0 μm).
To 2.5 μm, particularly preferably 1.5 to 2.5 μm)
Is preferably within the range. The total thickness of the magnetic tape is 3 to 10 μm (preferably 4.0 to 9.5 μm).
m, more preferably 4.5 to 9.0 μm, and particularly preferably 5.0 to 8.5 μm). The thickness of the back coat layer is 0.1 to 1.0 μm (more preferably 0.2 to 0.8 μm, particularly preferably 0.3 to 1.0 μm).
0.6 μm).

The magnetic layer of the magnetic tape of the second embodiment has a thickness of 0.05 to 1.0 μm (preferably 0.1 to 1.0 μm).
1.0 μm, more preferably 0.1 to 0.5 μm, particularly preferably 0.1 to 0.4 μm). The nonmagnetic layer has a thickness of 0.5 to 2.5 μm (preferably 1.0 to 2.5 μm, more preferably 1.5 to 2.5 μm).
2.0 μm, particularly preferably 1.5 to 1.8 μm). The ratio of the thickness of the magnetic layer to the thickness of the non-magnetic layer is
1: 2 to 1:15 (more preferably 1: 3 to 1: 1
It is preferably in the range of 0). It is preferable that the entire thickness of the magnetic tape of the second aspect and the thickness of the back coat layer are in the same range as the magnetic tape of the first aspect.

[0059]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples. “Parts” shown below represent “parts by weight” unless otherwise specified.

[Example 1] [Preparation of coating solution for forming magnetic layer] (Component for forming magnetic layer) 100 parts of ferromagnetic metal powder Coercive force (Hc): 1650 Oersted (Oe) Specific surface area by BET method: 56 m ² / G Crystallite size: 170 ° Saturated magnetization (σs): 130 emu / g Particle size (average major axis diameter): 0.2 μm Needle ratio: 7.0 pH: 9.0 Water-soluble Na: 70 ppm Water-soluble Ca: 10 ppm water-soluble Fe: 10 ppm] Magnetic substance surface treatment agent: phenylphosphonic acid 3 parts Polar group (-SO ₃ K group) -containing vinyl chloride copolymer 10 parts -SO ₃ K group content: 5 × 10 ^-6 mol / G, degree of polymerization 350 Epoxy group content: 3.5% by weight in monomer units (MR-110, manufactured by Zeon Corporation) 2.5 parts of a polyester polyurethane resin containing a polar group (—SO ₃ Na group) Pentyl glycol / caprolactone polyol / diphenylmethane-4,4′-diisocyanate (MDI) = 0.9 / 2.6 / 1 (weight ratio) —SO ₃ Na group content: 1 × 10 ⁻⁴ mol / g α− Alumina (particle size: 0.3 μm) 10 parts Nichrome trioxide 1 part Carbon black (particle size: 0.10 μm) 3 parts Methyl ethyl ketone 150 parts Cyclohexanone 50 parts

After kneading the above components with a continuous kneader,
It was dispersed using a sand mill. To the obtained dispersion, 2.5 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) and the following components were added and mixed well, and then, using a filter having an average pore diameter of 1 μm. After filtration, a coating solution for forming a magnetic layer was prepared. Butyl stearate 1 part Stearic acid 2 parts Oleic acid 1 part Toluene 40 parts

[Preparation of Backcoat Layer Forming Coating Solution] (Backcoat Layer Forming Component) Fine Particulate Carbon Black Powder 100 parts (manufactured by Cabot Corp., BP-800, average particle size: 17 mμ) Coarse particle carbon black powder 10 parts (manufactured by Kerncarb, thermal black, average particle size: 270 mμ) α-alumina (hard inorganic powder) 5 parts (average particle size: 200 mμ, Mohs hardness: 9) Nitrocellulose resin 140 parts Polyurethane resin 5 parts Polyisocyanate 40 Part (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) 5 parts polyester resin Dispersant: 5 parts copper oleate 5 parts copper phthalocyanine 5 parts barium sulfate 5 parts BF-1, average particle diameter: 50 mμ, Mohs hardness 3, Sakai Chemical Industry Methyl ethyl ketone 2200 parts Butylacetate 300 parts

Each component forming the back coat layer was kneaded with a continuous kneader, and then dispersed using a sand mill. After 600 parts of toluene was added to the obtained dispersion and mixed well, the mixture was filtered using a filter having an average pore diameter of 1 μm to prepare a coating liquid for forming a back coat layer.

[Preparation of Magnetic Tape] A support made of polyethylene naphthalate (PEN) [thickness: 6.] so that the thickness of the magnetic layer after drying the obtained coating solution for forming a magnetic layer is 2.0 μm. 0 μm, Young's modulus in the length (MD) direction 900 k
g / mm ² , Young's modulus in the width (TD) direction 580 kg / m
m ² , the center line average surface roughness Ra (cutoff value: 0.25 mm) of the magnetic layer applied surface is 6 nm]. Next, while the magnetic layer was still in a wet state, orientation treatment was performed using a cobalt magnet having a magnetic flux density of 3000 Gauss and a solenoid having a magnetic flux density of 1500 Gauss.
Thereafter, the magnetic layer was formed by drying (step 1).

After that, the above-mentioned coating solution for forming a back coat layer is applied to the other side of the support (the side opposite to the magnetic layer) so that the thickness after drying becomes 0.4 μm, and dried. A backing layer was provided, and a magnetic recording laminated body roll was obtained in which a magnetic layer was provided on one surface of the support and a backcoat layer was provided on the other surface (Step 2).

The obtained magnetic recording laminate roll was heated at a temperature of 11
In a heat treatment zone at 0 ° C., a tension of 3.0 kg / m for 5
After running for 2 seconds, a heat treatment was performed. Thereafter, the roll after the heat treatment is further processed into a seven-stage calendering machine (temperature: 90 ° C., linear pressure: 300 kg / cm) composed of only metal rolls
² ) Perform a calendar process through 5), tension 5kg
/ M (Step 3).

The obtained magnetic recording laminate roll was heated at 70 ° C.
Heat treatment was performed for 48 hours. Next, the magnetic recording laminate roll after the calendering treatment was slit into a width of 1/2 inch to obtain a magnetic tape for computer data recording according to the present invention (hereinafter, simply referred to as a magnetic tape). The obtained magnetic tape was placed in a 3480 type 1/2 inch cartridge for 580
m (Step 4).

[Example 2] and [Example 3] In Example 1, the backcoat layer was coated so that the thickness after drying was 0.3 µm (Example 2) or 0.5 µm (Example 3). A magnetic tape according to the present invention was produced in the same manner except for the following.

[Example 4] In Example 1, a support made of polyethylene naphthalate (PEN) [thickness: 6.0 µm]
m, Young's modulus in the length (MD) direction 800 kg / mm ² ,
A magnetic tape according to the present invention was produced in the same manner except that the Young's modulus in the width (TD) direction was changed to 650 kg / mm ² ].

Example 5 In Example 1, the nitrocellulose resin of the back coat layer was replaced with a polar group-containing vinyl chloride copolymer (—SO ₃ K group content: 5 × 10 ⁻⁶ mol /
g, a degree of polymerization of 350, and an epoxy group content of 3.5% by weight in a monomer unit).

Example 6 In Example 1, the nitrocellulose resin of the back coat layer was replaced with a phenoxy resin (PK).
HH, manufactured by Union Carbide Co.) to produce a magnetic tape according to the present invention.

Comparative Example 1 A magnetic tape for comparison was produced in the same manner as in Example 1, except that the backcoat layer was applied so that the thickness after drying was 0.7 μm.

[Comparative Example 2] In Example 1, a support made of polyethylene terephthalate (PET) [thickness: 6.0]
μm, Young's modulus in the length (MD) direction 760 kg / mm
^2. A magnetic tape for comparison was produced in the same manner except that the Young's modulus in the width (TD) direction was changed to 400 kg / mm ² ].

Comparative Example 3 A support made of polyethylene naphthalate (PEN) in Example 1 [thickness: 6.0 μm]
m, Young's modulus in the length (MD) direction 700 kg / mm ² ,
A magnetic tape for comparison was produced in the same manner except that the Young's modulus in the width (TD) direction was changed to 750 kg / mm ² ].

Comparative Example 4 A comparative magnetic tape was prepared in the same manner as in Example 1, except that the heat treatments I and II in Steps 3 and 4 were not performed.

[Comparative Example 5] In Example 1, the tension of the magnetic tape at the time of performing the heat treatment I in Step 3 was reduced to 7
A magnetic tape for comparison was produced in the same manner except that the weight was changed to kg / m.

Comparative Example 6 A comparative magnetic tape was prepared in the same manner as in Example 1, except that the heating temperature in the heat treatment II in Step 4 was changed to 40 ° C. The characteristics of the above magnetic tape are shown in Table 1 below.

[0078]

[Table 1] Table 1 ──────────────────────────────────── Tape Backcoat layer Young of support Rate (kg / mm ² ) Total thickness Thickness Length direction Width direction Support (μm) (μm) Binder (MD) (TD) MD / TD material ───────────── ─────────────────────── Example 1 8.4 0.4 A Formulation 900 580 1.55 PEN Example 2 8.3 0.3 A Formulation 900 580 1.55 PEN Example 3 8.5 0.5 A Formulation 900 580 1.55 PEN Example 4 8.4 0.4 Formulation 800 650 1.23 PEN Example 5 8.4 0.4 Formula B 900 580 1.55 PEN Example 6 8.4 0.4 Formula C 900 580 1.55 PEN ─────────────────────── Comparative Example 1 8.7 0.7 A formulation 900 580 1.55 PEN Comparative Example 2 8.4 0.4 A Formulation 760 400 1.9 PET Comparative Example 3 8.4 0.4 A Formulation 700 750 0.93 PEN Comparative Example 4 8.4 0.4 Formulation A 900 580 1.55 PEN Comparative Example 5 8.4 0.4 A formulation 900 580 1.55 PEN Comparative Example 6 8.4 0.4 A formulation 900 580 1.55 PEN処方 Formulation A: Binder mainly composed of nitrocellulose resin B Formulation: Binder mainly composed of polar group-containing vinyl chloride copolymer C Formulation: mainly composed of phenoxy resin Binder

[Production of Magnetic Recording / Reproducing System] Thin-Film Magnetic Head Recording Head Structure: An inductive head in which a two-turn thin-film coil is sandwiched between Co-based amorphous magnetic thin-film yokes. Track width: 25 μm, gap length: 1.0 μm Reproducing head Structure: Double seal SAL bias MR (magnetoresistive) head. The MR element is a Fe / Ni (permalloy) alloy thin film. Track width: 12.5 μm, shield interval: 0.3 μm The above recording / reproducing head was mounted on a Fujitsu F613A (34
80 type 1/2 inch cartridge magnetic recording / reproducing apparatus) to produce a magnetic recording / reproducing system.

[Evaluation as Magnetic Tape] The obtained magnetic tape was evaluated by the following evaluation method. (1) Measurement of the radius of curvature of the curl in the length direction of the magnetic tape A magnetic tape of 1/2 inch (1.27 cm) wide and 1 m long was placed in a test environment (23 ° C. ± 2 ° C., 50% ± 10% RH). After fixing one end and hanging the other end as a free end for 3 hours,
A measurement sample was prepared by cutting out a length of 35 mm below the center thereof, and the radius of curvature of the curl generated when the measurement sample was placed on a flat surface with the side of the tape facing down was measured.

(2) Measurement of radius of curvature of curl in the width direction of magnetic tape A magnetic tape having a width of 1/2 inch (1.27 cm) and a length of 1 m was placed in a test environment (23 ° C. ± 2 ° C., 50% ± 10% RH). ) Is fixed at one end, and the other end is suspended at the free end for 3 hours.
The sample is cut out so that the length above and below the center thereof is 500 mm in a length of 250 mm each. As shown in FIG. 1 of the accompanying drawings, one end of the tape is fixed with the magnetic layer facing upward, and a roller (diameter: 10 mm)
A 3.5 g weight is hung on the other end via the. The distance between the fixed end of the tape and the center of the roller is 200 mm. At 100 mm from the fixed end of the tape, scan the optical displacement meter in the width direction of the tape to measure the difference between the center position in the width direction of the tape and the position of the edge of the tape. The radius of curvature was measured.

(3) Winding upside down in the slitting process After the tape was slit in the slitting process, it was checked whether the tape was wound upside down. (4) Measurement of Output of Central Track A magnetic tape was mounted on the magnetic recording / reproducing system, and the tape was run at a tape speed of 2 m / sec and a running tension of 100 g. The position of the recording / reproducing head was set at 6.3 mm from the lower edge of the tape, and the output when a signal having a recording wavelength of 0.54 μm was recorded was measured. The evaluation was performed with the output value of the center track of Example 1 set to 100% and the relative evaluation was made.

(5) Measurement of Edge Track Output A magnetic tape was mounted on the magnetic recording / reproducing system, and the tape was run at a tape speed of 2 m / sec and a running tension of 100 g. The position of the recording / reproducing head was set at 0.8 mm from the lower edge of the tape, and the output when a signal having a recording wavelength of 0.54 μm was recorded was measured. The evaluation was performed based on the same criteria as in the above (4).

(6) Measurement of Vertical Movement of Tape A magnetic tape was mounted on the magnetic recording / reproducing system, and the tape was run at a tape speed of 2 m / sec and a running tension of 100 g. The vertical movement of the running tape edge was measured by measuring the position of the upper edge of the tape using an optical sensor on the reproducing head machine reel. The vertical movement of the tape was represented by the difference (μm) between the highest value and the lowest value of the position of the tape edge after one reciprocating pass.

(7) Measurement of Tape Thickness Ten tapes were stacked and the thickness was measured using a micrometer. The measured value was divided by 10 to obtain the tape thickness. Table 2 shows the evaluation results.

[0086]

[Table 2] Table 2 曲 Curl radius of curvature Turn over Playback output ( %) Tape length direction Width direction Central edge in curled state Vertical movement (mm) (mm) direction Winding track Track (μm) ─────────────────── １ Example 1 20 50 No protrusion on magnetic layer 100 96 5 Example 2 25 65 No protrusion on magnetic layer 100 98 4 Example 3 18 42 No protrusion on magnetic layer 98 94 6 Example 4 25 55 Magnetic layer no protrusion 97 97 4 Example 5 25 180 Magnetic layer no protrusion 100 99 2 Example 6 20 180 Magnetic layer no protrusion 100 99 2}比較 Comparative Example 1 16 30 Magnetic layer convex None 96 75 62 Comparative Example 2 6 48 Magnetic layer convex occurrence 75 73 6 Comparative Example 3 8 52 Magnetic layer convex occurrence 78 77 5 Comparative Example 4 630 Magnetic layer convex occurrence 75 62 55 Comparative Example 5 8 38 Magnetic layer convex occurrence 78 70 40 Comparative Example 6 7 33 Protrusion of magnetic layer raised 78 70 35 ────────────────────────────────────

From the results shown in Table 1 above, the magnetic tape according to the present invention (Examples 1 to 6) in which the curl in the length and width directions of the tape was adjusted to a predetermined radius of curvature or more, showed that the center track and There is little decrease in the reproduction output at the edge track, it shows good electromagnetic conversion characteristics, and there is little up and down movement of the tape during running, showing good running performance.In addition, after slitting, the tape is wound upside down. It can be seen that they have good handling characteristics without being taken off. In particular, in Examples 5 and 6, since a nitrocellulose resin having a large shrinkage force was not used for the back coat layer, the curl in the width direction was particularly weak, and the output was reduced and the vertical movement of the tape during running was very small. It can be seen that they have good electromagnetic conversion characteristics and running performance.

On the other hand, in the case of the magnetic tape of Comparative Example 1,
Because the backcoat layer is thicker, the curl in the length and width directions due to the shrinkage of the backcoat layer becomes stronger, and in particular, the curl in the width direction becomes stronger, resulting in poor head contact at the edge track and lower output. The vertical movement of the tape has also been increased due to the ease of the tape guide regulation. Since the curl in the length direction was relatively weak, no rewinding after the slit was performed. In the case of the magnetic tapes of Comparative Examples 2 and 3, since the Young's modulus in the length direction of the tape was low, the curl in the length direction was strong. For this reason, the head contact in the center track and the edge track became poor, and the output decreased. In addition, winding in an inverted state after the slit occurred. However, since the curl in the width direction is weak, the vertical movement of the tape is small. Comparative Examples 4 and 5
In the case of the magnetic tapes Nos. 6 and 7, the curl is strong in both the length direction and the width direction, and the head contact at the center track and the edge track is poor, so that a sufficient reproduction output cannot be obtained. In addition, the tape moved greatly up and down during running, and the tape was turned upside down after slitting.

Example 7 A coating solution for forming a magnetic layer and a coating solution for forming a backcoat layer were prepared in the same manner as in Example 1.

[Preparation of Non-Magnetic Layer-Forming Coating Solution] (Non-Magnetic Layer-Forming Component) Non-magnetic Powder TiO ₂ (rutile type) 90 parts TiO ₂ content: 90% or more Average primary particle diameter: 0.035 μm BET The specific surface area of ^{law: 40m 2 / g pH: 7.0} DBP oil absorption: 27~38g / 100g Mohs hardness: 6.0 surface coating compound (A1 ₂ 0 _3): 1.5 wt% carbon black (Mitsubishi carbon ( Co., Ltd.) 10 parts Average primary particle diameter: 16 μm DBP oil absorption: 80 ml / 100 g pH: 8.0 Specific surface area by BET method: 250 m ² / g Volatile content: 1.5% Polar group (—SO ₃ K group, Epoxy group-containing vinyl chloride resin 12 parts (MR-110, manufactured by Zeon Corporation) Polar group (-SO ₃ Na group) -containing polyester polyurethane resin 5 parts Neopentyl glycol / capro Lactone polyol / diphenylmethane-4,4′-diisocyanate (MDI) = 0.9 / 2.6 / 1 (weight ratio) —containing 1 × 10 ⁻⁴ mol / g of SO ₃ Na groups 150 parts of methyl ethyl ketone 50 parts of cyclohexanone

After the above components were kneaded with a continuous kneader, they were dispersed using a sand mill. To the obtained dispersion, 3 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added, and the following components were further added and mixed well, and then filtered using a filter having an average pore diameter of 1 μm. A coating solution for forming a non-magnetic layer was prepared. Butyl stearate 1 part Stearic acid 2 parts Oleic acid 1 part Toluene 40 parts Butyl acetate 40 parts

[Preparation of Magnetic Tape] In the first embodiment,
The obtained coating solution for forming a nonmagnetic layer and the coating solution for forming a magnetic layer are coated so that the thickness of the dried nonmagnetic layer is 1.8 μm, and the thickness of the dried magnetic layer is further reduced on this. By performing simultaneous multi-layer coating on the support used in Example 1 so as to have a thickness of 0.2 μm, the magnetic tape for computer data recording according to the present invention was prepared in the same manner except that the non-magnetic layer and the magnetic layer were provided. Manufactured. The entire thickness of the obtained magnetic tape was 8.4 μm.

[Comparative Example 7] In Example 7, a support made of polyethylene naphthalate (PEN) [thickness: 6.0 µm]
m, Young's modulus in the length (MD) direction 700 kg / mm ² ,
A magnetic tape for comparison was produced in the same manner except that the Young's modulus in the width (TD) direction was changed to 400 kg / mm ² ]. The entire thickness of the obtained magnetic tape was 8.4 μm.

[Evaluation as Magnetic Tape] The magnetic tapes obtained in Example 7 and Comparative Example 7 were evaluated according to the evaluation method described above. Table 3 shows the evaluation results.

[0095]

[Table 3] ──────────────────────────────────── Curl radius of curvature Turn over Playback output ( %) Tape length direction Width direction Central edge in curled state Vertical movement (mm) (mm) direction Winding track Track (μm) ─────────────────── {Example 7 20 48 Magnetic layer convex None 140 135 5} {Comparative Example 7 8 55 Generation of Protrusion of Magnetic Layer 90 85 5} ─────────────

From the results shown in Table 3 above, even in the case of the magnetic tape in which the non-magnetic layer and the magnetic layer are provided on the support (Example 7), the curl in the length direction and width direction of the tape can be reduced to a predetermined curvature. By adjusting the radius or more, it is shown that the electromagnetic conversion characteristics in the center track and the edge track are good, and the tape does not move up and down during running, showing good running performance. Later, it can be seen that the tape is not wound up inside out and has good handling characteristics. On the other hand, in the case of Comparative Example 7, as the Young's modulus of the support was reduced, curling was likely to occur, particularly in the length direction of the tape.
The contact with the head deteriorated, and the output decreased. Also, the handling properties were poor.

[0097]

The magnetic tape of the present invention is adjusted so that the curl in the length and width directions is equal to or larger than a predetermined radius of curvature. Also, there is little drop in output and vertical movement of the tape during running, so that good electromagnetic conversion characteristics and running characteristics can be obtained.In manufacturing, the tape is not turned upside down after slitting, and handling is performed. The properties are also well maintained. Therefore, it can be said that the magnetic tape is suitable for a recording / reproducing system for high-density recording. In particular, it is a magnetic tape that is advantageous for computer data recording.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method of measuring a radius of curvature of a curl in a width direction of a magnetic tape.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Minoru Iki 2-12-1, Ogimachi, Odawara-shi, Kanagawa F-term in Fuji Photo Film Co., Ltd. 5D006 BA19 BB07 CB07 CC01 DA00 FA02 FA05 FA09

Claims (3)

[Claims] 1. The overall thickness of a long support having a magnetic layer containing ferromagnetic powder and a binder on one side and a backcoat layer containing carbon black and a binder on the other side. Is a magnetic tape of 3 to 10 μm, the radius of curvature of the curl in the longitudinal direction of the magnetic tape is 10 mm or more, and the curl in the width direction of the tape has a convex curve toward the magnetic layer side, A magnetic tape having a radius of curvature of 40 mm or more. 2. A substantially non-magnetic material comprising a non-magnetic powder and a binder on one side of an elongated support having a thickness of 0.5 to 0.5.
A 2.5-μm non-magnetic layer and a 0.05-1.0 μm-thick magnetic layer containing a ferromagnetic powder and a binder in this order;
A magnetic tape having a back coat layer containing carbon black and a binder on the other side and having a total thickness of 3 to 10 μm, wherein the radius of curvature of the magnetic tape in the longitudinal direction is 10 mm or more, and A magnetic tape characterized in that the tape has a curl in the width direction that is convex toward the magnetic layer side and has a radius of curvature of 40 mm or more. 3. The Young's modulus in the longitudinal direction of the support is 1.1 to 1.8 times the Young's modulus in the width direction, and the Young's modulus in the longitudinal direction is 750 to 950 kg / mm ^2. 3. The magnetic tape according to 1 or 2.